In order to improve the combustion process within combustion chamber space of an internal combustion engine for meeting certain objective criteria, especially those related to tailpipe emissions, it is generally accepted that liquid fuel should be atomized as finely as possible. Numerous and various measures have been proposed toward this end, including for example, heater attachments and air assist attachments. Such attachments naturally require additional parts, not only at the fuel injector, but also often leading to the fuel injector. Added cost and complexity are a necessary result. Strictly mechanical means in only the fuel injector itself for accomplishing improved fuel atomization would therefore seem to be a preferred solution, and the present invention relates to such a means, although it should be understood that usage of a fuel injector embodying principles of the invention could occur in conjunction with accessory devices, such as those mentioned above.
Traditionally, fuel injectors are designed to present laminar flow fluid to its metering components. Although this results in clearly defined streams exiting the fuel injector, it also results in large droplet size and poor atomization. Certain prior techniques to improve atomization have created turbulent flow upstream of the metering components, supplying angular momentum to the fuel that results in better fuel break-up at the metering components.
Prior forms of strictly mechanical means for improving fuel atomization are shown in a number of patents, including U.S. Pat. Nos. 4,628,576; 4,647,013; 4,756,508; 4,808,260; 4,826,131; 4,907,748; 4,934,653; and 5,286,002. Commonly assigned U.S. Pat. No. 4,934,653 discloses two flat orifice disk members stacked together. These orifice disk members are stainless steel and are fabricated by mechanical metalworking processes. The devices of many of the other patents comprise silicon structures, and they are typically fabricated by silicon micromachining techniques. The reader will notice that the silicon micromachined devices are integrated with the valve mechanism itself, whereas in a fuel injector, as in U.S. Pat. No. 4,934,653, the orifice disk members are non-integrated, being disposed downstream of the valve seat, just before the nozzle at which fuel is injected from the fuel injector. The fabrication of the silicon micromachined structures requires rather sophisticated, and hence costly, processing techniques and equipment. Moreover, dimensioning and tolerancing of the silicon micromachined structures is somewhat critical, but it has been recognized that certain silicon micromachined structures can provide fuel atomization that meets certain more stringent criteria, but at a disadvantage of adding to the unmetered fuel under certain engine conditions due to increased sac volume of the fuel injector. This unmetered fuel can create exhaust emission problems if not properly calibrated out. In view of the foregoing, it would therefore seem to be significantly advantageous if a fuel injector could accomplish the desired improved fuel atomization by using metal orifice disks, stainless steel disks for example, that do not increase the sac volume and that do not require the use of micromachining techniques like those required to produce the aforementioned silicon micromachined structures but rather are fabricated by metalworking techniques, such as those employed in U.S. Pat. No. 4,934,653 for fabricating orifices disks, and such advantages are present in the present invention.
Accordingly, in one comprehensive aspect the present invention may be said to relate to a fuel injector for injecting fuel into an internal combustion engine comprising a body, a fuel passageway through the body leading to a nozzle from which fuel is injected, a valve seat circumscribing an opening and disposed internally of the body within the passageway, an electrically operated mechanism comprising a valve element that is reciprocated relative to the valve seat to close and open the passageway to flow by seating and unseating the valve element on and from the valve seat to close and open the circumscribed opening through the valve seat, and orifice disk means disposed in the passageway between the valve seat and the nozzle, characterized in that said orifice disk means comprises two orifice disk members stacked face-to-face to mutually abut around their perimeters but are shaped in their central regions to cooperatively define between themselves a walled chamber space, each orifice disk member comprises at least one through-orifice extending through the wall of the chamber space to place the chamber space in fluid communication with the fuel passageway so that fuel that has passed through the valve seat opening passes through the chamber space before it is injected from the nozzle, and collectively the orifices perform turbulence-creating, metering, and targeting functions, although any particular orifice may perform primarily only one of these functions or a combination of two or more of these functions.
Within this comprehensive aspect, the fuel injector is characterized further: in that in certain species of the invention the at least one through-orifice in the one orifice disk member comprises plural such through-orifices, and the at least one through-orifice in the other orifice disk member comprises plural such through-orifices, and further in that each one of the through-orifices in the one orifice disk member has a larger flow area than each one of the through-orifices in the other orifice disk member; in that in certain species of the invention the at least one through-orifice in one of the orifice disk members has a larger flow area than the at least one through-orifice in the other of the orifice disk members, and further in that in some of these species said one orifice disk member is upstream of the other while in other of these species said other orifice disk member is upstream of said one orifice disk member; in that in certain species of the invention the central region of a particular orifice disk member is fiat while the central region of the other orifice disk member is not fiat, and further in that in some of these species of the invention, the orifice disk member whose central region is fiat is disposed upstream of the other orifice disk member while in other of these species, it is disposed downstream; in that in certain species of the invention a third orifice disk member is disposed sandwiched between the one and the other orifice disk members to divide the chamber space into two portions and comprises its own at least one through-orifice for placing the two portions of the chamber space in fluid communication with each other; in that in certain species of the invention the at least one through-orifice in one of the orifice disk members is organized and arranged to create primarily turbulent flow, and the at least one through-orifice in the other of the orifice disk members primarily meters the flow, and further in that in some of these species it is the upstream disk that primarily meters the flow and the downstream disk that primarily creates turbulence flow while in other of these species it is the downstream disk that primarily meters the flow and the upstream disk primarily creates turbulent flow. Targeting of the injected fuel toward a target that is spaced from the fuel injector's nozzle is accomplished primarily be the most downstream disk, but it is possible for an upstream disk to have some influence on targeting depending on specific disk and orifice configurations. The foregoing, and further aspects, features, and advantages, may be seen in the following detailed description of a presently preferred embodiment of the invention that is accompanied by drawings illustrating the best mode contemplated at this time for carrying out the invention.